s 


CONNECTICUT 


43 

rr  o  2) 

AGRICULTURAL  EMRIMEHT  STATION  ^-'^^ 


NE"W    HAVEN,    CONN. 


BULLETIN    177,  AUGUST,  1913^^^^ 


ENTOMOLOGICAL  SERIES 


^^>;„ 


THE  APPLE-TREE  TENT-CATP^I\1aR^^ 


CONTENTS.  Page 

Officers  and  Staff  of  Station 2 

Apple-tree  Tent-Caterpillar 3 

Evidence  of  Damage :  .  3 

Outbreaks  in  Connecticut 4 

Distribution ■ 5 

Food  Plants . fi 

Habits  and  Life  History 7 

Description 10 

Mistaken  for  Other  Insects 11 

The  Forest  Tent-Caterpillar  and  how  it  difTers 13 

Natural  Enemies 14 

Control  Measures 15 

Destroying  the  Egg-clusters 15 

Removing  the  Nests 16 

Spraying 17 

Community  Effort 17 

Summary 19 

The  Bulletins  of  this  Station  are  mailed  free  to  citizens  of  Con- 
necticut who  apply  for  them,  and  to  others  as  far  as  the  editions 
permit. 


CONNECTOT  AGRICULTDML  EXPERIMENT  STATION. 


OE^IFICEIiS    -A^nsriD,  ST-A-IFiF. 


BOARD  OF  CONTROL. 

His  Excellency,   Simeon  E.  Baldwin,  ex  officio,  President. 

Prof.  H.  W.  Conn,  Vice  President Middletown 

GEO^Gf  A.  HopsoN,^'  Secretary Wallingford 

E.  H.  Jenkins,  Director  and  Treasurer New  Haven 

Joseph  W.'  Als.op Avon 

Wilson  H.  Lee.  :M Orange 

Frank  H.  Stadtmueller Elmwood 

James  H.  Webb Hamden 


STATION    STAFF. 

Administration.  E.  H.  Jenkins,  Ph.D.,  Director  and  Treasurer. 

Miss  V.  K.  Cole,  Librarian  and  Stenographer. 
Miss  L.  M.  Brauti.echt,  Bookkeeper  and  Stenographer . 
William  Veitch,  In  Charge  of  Buildings  and  Grotinds. 

Chemistry. 

Analytical  Laboratory.     John  Phillips  Street,  M.S.,  Chetnist  in  Charge. 
E.  Monroe  Bailey,  Ph.D.,    C.  B.  Morison,-  B.S., 
C.  E.  Shepard,  G.  L.  Davis,  Assistants. 
Hugo  Lange,  Laboratory  Helper. 
V.  L.  Churchill,  Sampling  Agent. 
Miss  E.   B.  Whittlesey,  Stenographer. 


Proteid  Research. 


T.  B.  Osborne,  Ph.D.,  Chemist  in  Charge. 
Miss  E.  L.  Ferry,  M.S.,  Assistant. 


G.  P.  Clinton,  S.D.,  Botanist. 

E.  M.  Stoddard,  B.S.,  Assistant. 

Miss  M.  H.  Jagger,  Seed  Analyst. 

Miss  E.  B.  Whittlesey,  Herbarium  Assistant. 


Entomology. 


W.  E.  Britton,  Ph.D.,  Entomologist ;  also  State 

Entomologist. 
B.  H.  Walden,  B.Agr.,  Q.  S.  Lowry,  B.S.,  Assistants. 
Miss  F.  M.  Valentine,  Stenographer. 


Forestry. 


Walter  O.  Filley,  Forester;  also  State 

Forester  and  State  Forest  Fire  Warden, 
A.  E.  Moss,  M.F.,  Assistant  Station  Forester. 
Miss  E.  L.  Avery,  Stenographer. 


Plant  Breeding. 


H.  K.  Hayes,  M.S.,  Plant  Breeder. 
C.  D.  HuBBELL,  Assistant. 


THE  APPLE-TREE  TENT-CATERPILLAR. 

Malacosoma  (Clisiocampa)  americana  Fabr. 
By  W.  E.  Britton,  State  Entomologist. 

This  bulletin  is  called  forth  by  the  unusual  abundance  in  Con- 
necticut in  1913  of  the  apple-tree  or  orchard  tent-caterpillar,  the 
outbreak  covering  the  entire  state  except  for  certain  localities 
along  the  coast. 

Bulletin  139,  dealing  with  this  insect,  was  issued  in  1902,  but 
the  supply  was  soon  exhausted,  and  for  several  years  it  has  been 


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Figure  i. — Apple  tree  almost  defoliated,  near  Waterbury. 


out  of  print.  To  furnish  information  and  to  point  out  the  simple 
control  methods  is  the  object  of  the  present  bulletin,  which  is  more 
than  a  revised  edition  of  bulletin  139,  as  much  of  it  has  been 
rewritten  and  most  of  the  illustrations  are  new. 

Evidence  of  Damage. 
The  conspicuous  white  nests  of  the  apple-tree  tent-caterpillar 
during  the  month   of   May   show   everybody   that   the   insect  is 


4         CONNECTICUT    EXPERIMENT    STATION,    BULLETIN    NO.    IJJ . 

present.  Though  not  as  important  as  several  other  insect  pests 
of  the  orchard,  it  is  one  of  the  most  noticeable.  Its  destructive- 
ness,  however,  is  often  more  apparent  than  real.  In  ordinary 
seasons  the  caterpillars  feed  upon  several  species  of  wild  cherry 
and  do  little  harm  in  the  orchard,  though  trees  in  hedgerows 
and  along  the  highways  may  be  attacked.  Nevertheless,  it  causes 
some  damage  and  when  abundant,  as  at  present,  many  apple  trees 
are  defoliated.  This  occurs  early  in  the  season  and  new  leaves 
are  put  forth,  but  this  weakens  the  trees  appreciably  and  should 
be  prevented,  if  possible. 

The  nests  are  always  unsightly  and  mar  the  beauty  of  the  land- 
scape even  if  only  worthless  trees  are  attacked.  The  control 
of  the  tent-caterpillar  is  not  difficult  and  there  is  no  reason  for 
allowing  it  to  multiply  unchecked.  We  should  remove  the 
worthless  trees  and  take  care  of  the  others. 

Outbreaks  in  Connecticut. 
Though  the  nests  are  seen  every  spring  in  Connecticut,  the 
insect  has  not  usually  been  as  destructive  here  as  in  northern 
New  England.  Normally  the  wild  cherry  furnishes  the  common 
food  supply,  and  often  the  injury  does  not  extend  to  apple 
orchards. 


Figure  2. — Egg-Cluster  of  apple  tree  tent-caterpillar.     Natural  size. 


In  1902,  however,  the  tent-caterpillar  was  abundant  every- 
where and  attacked  not  only  cherry  and  apple  trees,  but  several 
other  kinds.  One  grower  reported  this  as  the  most  troublesome 
pest  on  his  peach  trees.  The  black  cherry  trees  and  choke  cherry 
bushes  along  roadsides  and  hedgerows  were  stripped  of  leaves. 
According  to  our  observations,  the  outbreak  was  not  a  local  one, 
but  occurred  over  the  whole  State,  though  somewhat  more  severe 
in  the  northern  portion.     The  three  agents  employed  that  year 


OUTBREAKS    IN    CONNECTICUT.  5 

by  the  Station  to  gather  fruit  statistics,  who  covered  the  entire 
State  in  their  travels,  reported  defoHated  trees  in  nearly  every 
town.  The  writer  also  made  similar  observations  in  those 
portions  of  the  State  in  which  he  had  occasion  to  travel. 

Moreover,  of  all  orchard  insects  the  tent-caterpillar  was  the 
most  commonly  reported  by  the  fruit  growers. 

The  late  Mr.  T.  S.  Gold  believed  that  the  insect  had  not  been 
so  abundant  for  sixty-six  years,  or  since  the  terrible  ice  storm 
of  1836,  as  in  1902. 

In  1903,  the  caterpillars  and  their  nests  were  very  numerous, 
though  perhaps  less  so  than  the  previous  year.  Mr.  J.  M.  Whit- 
tlesey of  Morris  wrote  that  in  his  neighborhood  he  had  never 
seen  the  nests  so  abundant,  but  that  most  of  the  caterpillars  died 
before  reaching  maturity.  For  several  years  after  this  outbreak, 
nests  of  the  tent-caterpillar  were  not  much  in  evidence.  A  few 
could  be  found  everywhere,  but  the  caterpillars  did  no  damage 
and  little  attention  was  paid  to  them.  In  191 1  and  1912  a  num- 
ber of  specimens  and  inquiries  regarding  them  were  received 
from  various  parts  of  the  State. 

Early  in  191 3  many  egg-clusters  were  sent  in,  and  when  the 
trees  put  out  their  leaves  in  May  it  was  evident  that  191 3  was 
a  "caterpillar  year,"  there  being  more  nests  or  tents  than  in 
any  year  since  1902.  In  New  Haven  the  nests  are  not  very 
abundant,  but  back  a  few  miles  from  the  coast  every  neglected 
apple  tree,  every  black  cherry  tree  and  every  choke  cherry  bush, 
bears  from  one  to  fifteen  or  twenty  nests,  and  many  apple  trees 
were  stripped  as  in  figure  i.  At  Stonington,  which  is  a  coast 
town,  the  caterpillars  are  extremely  abundant  and  many  trees  are 
stripped.  In  Litchfield  county  the  nests  are  very  abundant. 
They  are  so  reported  from  Salisbtn-y  and  Norfolk  and  the  writer 
observed  them  in  portions  of  Roxbury,  Woodbury  and  Washing- 
ton, as  well  as  in  Waterbury,  Middlebury  and  Southbury  of 
New  Haven  County.  Nearly  all  the  roadside  apple  and  wild 
cherry  trees  as  well  as  the  neglected  orchards  were  stripped.  In 
Newtown,  nests  were  so  abundant  that  prizes  were  offered  for 
their  destruction  as  is  described  on  page  18. 

Distribution. 
The  apple-tree  tent-caterpillar  is  a  native  of  North  America 
occurring  throughout  the   Eastern   United    States   and   Canada, 


6         CONNECTICUT    EXPERIMENT    STATION,    BULLETIN    NO.    I77. 

westward  to  the  Rocky  Mountains.  Damage  was  recorded  as 
early  as  1646,  and  at  irregular  intervals  the  species  became  so 
abundant  that  those  years  were  termed  "caterpillar  years"  by 
the  settlers.     These  periodical  outbreaks  have  doubtless  occurred 


Figure  3. — Nest  on  apple  tree. 

ever    since,   but   are   more  pronounced   and   noticeable   in    New 
England  than  in  other  parts  of  the  country. 

Food  Plants. 
The  black  and  choke  cherry  are  the  favorite  and  probably 
the  natural  food-plants  of  the  species.  The  apple  is  the  next 
choice,  and  in  seasons  when  the  caterpillars  are  numerous 
orchards  are  attacked  and  sometimes  entirely  defoliated.  Lowe 
mentions*  cherry,  apple,  plum,  peach,  rose,  witch  hazel,  beech, 
barberry,  oak,  wihow  and  poplar  as  food  plants.  Weed  found 
the  caterpillars   feeding  upon  birch,t  and  the  writer  has  occa- 


*  N.  Y.  Agr.  Exp.  Station,  Bulletin  152,  p.  281. 
fN.  H.  Agr.  Exp.  Station,  Bulletin  38,  p.  53. 


HABITS    AND    LIFE    HISTORY.  7 

sionally  found  them  eating"  the  leaves  of  various  species  of  oak. 
In  Woodbury,  this  season  the  writer  observed  the  old  nests  on 
oak  and  river  beech  (Carpinus). 

Habits  and  Life  History. 

The  eggs  are  laid  in  cylindrical  masses  encircling  small  twigs 
of  the  apple  and  cherry,  during  the  last  days  of  June  or  first 
of  July.  Specimens  in  breeding  cages  in  the  laboratory  laid 
eggs  soon  after  the  middle  of  June,  but  this  is  somewhat  earlier 
than  they  are  laid  upon  the  trees  out  of  doors.     After  deposit- 


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Figure  4. — Tent-Caterpillars.     Partially  grown.     Natural  size. 

ing  a  ring  of  eggs  averaging  over  two  hundred  in  number,  the 
parent  moth  covers  them  with  a  viscid  fluid  which  hardens, 
giving  them  a  varnished  appearance.  The  eggs  are  probably 
greatly  protected  by  this  coating  from  the  weather  and  from 
predaceous  insects.     See  figure  2. 

The  eggs  do  not  hatch  until  the  following  April,  thus  remain- 
ing upon  the  twigs  for  about  nine  months.  The  tiny  cater- 
pillars first  feed  upon  the  frothy  mass  surrounding  the  eggs, 
and  next  attack  the  new  leaves  which  are  then  unfolding. 
After  a  few  days  they  spin  many  silken  threads  to  form  their 
nest,  usually  in  a  fork  of  the  branches.  See  figure  3  and  front 
page  of  bulletin. 


8  CONNECTICUT    EXPERIMENT    STATION,    BULLETIN    NO.    I77. 


Figure  5. — Tent-Caterpillars  resting  on  the  outside  of  the  nest. 


HABITS    AND    LIFE    HISTORY.  9 

This  nest  or  colony  contains  the  caterpillars  from  a  single 
mass  of  eggs.  The  caterpillars  feed  in  fair  weather  in  the  morn- 
ing and  again  in  the  afternoon  and  according  to  Fitch  again  in 
the  night,  but  during  cloudy  weather  they  remain  in  the  nest. 
When  nearly  full-grown,  the  caterpillars  may  often  be  found  at 
rest  on  the  outside  of  the  tent  as  shown  in  figure  5.  They  spin 
threads  wherever  they  crawl  along  the  branches  from  the  nest 
to  their  feeding  places. 

The  egg-masses  do  not  all  hatch  at  the  same  time,  and  it  is 
not  uncommon  to  find  half-grown  and  newly-hatched  cater- 
pillars in  the  same  vicinity.     Mr.  J.  M.  Whittlesey,  of  Morris, 


Figure  6. — Cocoons   of  tent-caterpillar.     Natural   size. 


Conn.,  states  in  a  letter  to  the  writer,  that  during  the  spring  of 
1902  the  hatching  period  extended  over  nearly  twenty-one  days. 

The  average  feeding  period  is  about  six  weeks,  during  which 
time  the  caterpillars  have  molted  or  cast  their  skins  several 
times.  As  they  increase  in  size  they  become  more  voracious 
and  devour  the  leaves  rapidly.  At  each  molting  period  they 
stop  feeding  for  a  few  hours,  then  begin  again  with  renewed 
vigor. 

When  fully  grown  the  caterpillars  cease  eating  and  wander 
about  restlessly  for  a  day  or  two,  then  spin  white  silken  cocoons 
in  the  grass  under  the  trees,  in  the  crevices  of  the  rough  bark, 
or  about  buildings,  boxes,  etc.,  that  may  be  near  the  infested 
trees.     See  figure  6. 

There  is  only  a  single  brood  each  year. 


lO      CONNECTICUT    EXPERIMENT    STATION,    BULLETIN    NO.    1 77. 

A  colony  of  tent-caterpillars  was  brought  into  the  laboratory 
on  May  ist.  The  nest  had  been  formed,  though  the  cater- 
pillars were  small,  measuring  about  three-sixteenths  of  an  inch 
in  length  and  they  had  probably  been  hatched  about  a  week. 
On  May  26th,  they  had  become  full-grown  and  three  or  four 
pupated.  In  a  week  all  had  made  their  cocoons  and  by  the  i6th 
of  June  the  adults  began  to  emerge.  This  continued  for  nearly 
a  week,  until  all  had  come  forth.  Meantime  several  egg- 
masses  had  been  formed  in  the  breeding  cage  by  the  females. 

Description. 

Egg.  The  eggs  are  grey  in  color  and  very  small,  being 
about  one-eighteenth  of  an  inch  long,  and  slightly  more  than 
half  as  thick.  The  upper  end  is  circular,  and  is  slightly  larger 
than  the  lower  end.  They  are  placed  on  end,  close  together, 
and  covered  one-sixteenth  of  an  inch  deep  with  a  brown  substance 
resembling^  glue.  The  whole  mass  usually  encircles  the  twig, 
but  is  sometimes  deposited  on  one  side  only.  An  egg-mass  is 
shown  in  figure  2. 

Larva.  When  first  hatched,  the  caterpillar  is  very  small  and 
nearly  black  with  a  few  grey  hairs. 

It  molts  five  or  six  times  as  it  increases  in  size,  and  after 
each  molt  the  markings  show  more  distinctly.  When  full- 
grown  the  caterpillar  is  from  two  to  two  and  one-half  inches 
in  length  and  is  thinly  covered  with  long  light-brown  hairs. 

The  color  is  black  with  a  white  stripe  along  the  back,  and 
many  short  irregular  brownish  stripes  or  markings  along  the 
side  of  each  segment.  The  sides  are  of  a  bluish  color  and  each 
segment  bears  an  oval  blue  spot  nearly  surrounded  with  black. 
The  under  side  of  the  body,  head,  and  legs  are  black.  The 
larvae,  natural  size,  are  shown  in  figure  4. 

Pupa.  The  pupa  stage  is  passed  in  a  white,  oval  cocoon, 
which  is  about  one  inch  in  length  and  half  an  inch  in  thickness. 
It  is  made  of  silken  threads  spun  by  the  caterpillar  and 
loosely  woven.  It  is  usually  attached  by  one  side  to  some  object 
in  a  more  or  less  protected  place.  Figure  6  shows  a  few  of 
the  cocoons. 

Adult.  The  adult  is  a  four-winged  moth  of  light  reddish- 
brown  color  with  two  whitish  stripes,  extending  obliquely  across 


MISTAKEN    FOR    OTHER    INSECTS.  11 

each  fore  wing.  The  female  has  a  wing  expanse  of  about  one 
and  one-half,  and  the  male  about  one  and  one-eighth  inches. 
The  males  are  inclined  to  be  somewhat  darker  in  color  than  the 
females,  though  there  is  much  variation  in  the  intensity  of  the 
oTound  color  and  of  the  markings  in  both  sexes. 


Figure  7. — Adults.     Female  above.     Male  below.     Natural  size. 

The  rear  wings  are  the  same  color  as  the  fore  wings,  but 
are  not  marked  with  white  stripes.  Both  sexes  are  shown  in 
figure  7. 

Mistaken  for  Other  Insects. 

Notwithstanding  the  fact  that  the  tent-caterpillar  is  one  of 
the  best  known  and  most  familiar  of  all  our  injurious  insects, 
it  is  often  erroneously  called  "bag-worm."  "Bag-worm"  is  the 
common  name  for  Thyridopteryx  cphenierccformis  Haw.,  a  very 
different  insect  occurring  in  the  southern  states.  Each  larva  is 
inclosed  and  suspended  in  a  bag  or  sack  as  is  shown  in  figure 
8.  This  insect  is  found  in  Connecticut  chiefly  on  arborvitse, 
which  has  been  imported  from  the  South. 

Fruit  growers  are  apt  to  confuse  the  tent-caterpillar  with  the 
fall  web-worm,  Hyphantria  cunea  Drury,  an  insect  which  makes 
nests  on  the  ends  of  the  branches  of  fruit  and  forest  trees  later 
in  the  season.  The  two  species  are  quite  different  and  can 
readily  be  distinguished  if  we  remember  that  the  former  occurs 
only  in  spring  and  chiefly  in  the  crotches  of  the  trunk  or 
branches.     The  caterpillars  rem.ain  inside  the  nest  in  cloudy  and 


12       CONNECTICUT    EXPERIMENT    STATION,    BULLETIN    NO.    I//. 

stormy  weather,  but  go  out  to  feed.  The  latter  (fall  web-worm) 
is  partially  double  brooded  in  Connecticut,  and  a  few  nests  are 
seen  the  latter  part  of  June,  but  the  greater  number  of  the  main 


Figure  8. — The  bag-worm.     Natural  size. 

brood  do  not  appear  until  August  and  September.  The  feeding 
is  done  within  the  web  which  encloses  the  food  leaves.  After 
these  have  been  eaten,  the  web  is  enlarged  to  include  fresh  leaves 


Figure  g. — Nests  of   fall  web-worm.      (After   Slingerland.) 


MISTAKEN    FOR   OTHER    INSECTS.  13 

which  in  turn  are  devoured.  In  this  way  sometimes  an  entire 
branch  is  enclosed  in  the  nest  of  the  fall  web-worm,  which  is 
always  first  formed  at  the  end  of  a  branch,  as  is  shown  in 
figure  9- 

The  apple-tree  tent-caterpillar  is  also  mistaken  for  the  forest 
tent-caterpillar,  but  the  difference  and  relationship  are  explained 
below. 

The  Forest  Tent-Caterpillar  and  How  It  Differs. 

The  forest  tent-caterpillar,  Malacosoma  disstria  Hbn.,  makes 
no  nest  or  tent  and  during-  most  of  the  larval  period  the  cater- 


FiGURE  10. — Forest  tent-caterpillars.     Natural  size. 

pillars  feed  singly  or  independently.  When  nearly  full  grown, 
however,  they  cluster  on  the  trunks  of  trees  in  much  the  same 
manner  as  the  apple-tree  tent-caterpillars  gather  on  the  outside 
of  the  nest.  The  forest  species  feeds  upon  fruit,  shade  and 
forest  trees,  and  at  various  times  it  has  defoliated  large  areas 
in  Vermont,  New  Hampshire  and  Northern  New  York.  In  fact 
there  has  been  injury  in  New  York  and  on  Long  Island  the 
present  season. 

The  forest  tent-caterpillar  is  generally  light  blue  in  color  with 
a  row  of  white  keyhole-shaped  spots  along  the  back  instead  of 
a  stripe.  The  caterpillar  is  shown  in  figure  lo  and  the  egg- 
cluster  shown  in  figure  ii  has  the  ends  squared  oft"  and  less 
pointed  than  that  of  the  apple-tree  species  shown  in  figure  12. 


14    connecticut  experiment  station,  bulletin  no.  i'j'j. 

Natural  Enemies. 

The  tent-caterpillar  is  usually  held  in  check  by  its  natural 
enemies;  in  fact,  but  for  them  it  would  be  much  more  abundant 
and  destructive  each  season.  Its  abundance  the  present  season 
and  in  other  "caterpillar  years"  is  undoubtedly  due  to  a  com- 
parative scarcity  of  natural  enemies,  thus  allowing  the  species 
to  multiply  unchecked. 

Conspicuous  among  these  enemies  are  the  four-winged 
ichneumon  flies  and  a  bacterial  disease  called    "wilt." 


Figure  ii. — Egg-cluster  of  forest 
tent-caterpillar.     Natural  size. 


Figure  12. — Egg-cluster  of  apple 
tree  tent-caterpillar.     Natural  size. 


Quaintance*  mentions  three  egg  parasites,  Telenomus  clisio- 
campce  Riley,  Pteromalus  sp.  and  Platygaster  sp.,  which  attack 
the  egg-clusters  of  the  apple-tree  tent-caterpillar.  Most  of  the 
parasites  attack  the  larvae  and  pupae  and  Fiskef  recorded  24 
species  of  insects  reared  from  the  tent-caterpillar.  Some  of 
these  were  undoubtedly  secondary  or  hyper-parasites,  but  four 
species  of  Pimpla,  three  species  of  Apanteles,  and  one  tv/o- 
winged  fly,  F rontina  frenchii  Will.,  are  probably  primary  parasites. 


*  Bureau  of  Entomology,  Circular  98,  page  5,  1908. 

t  New  Hampshire  Agr.  Exp.  Sta.,  Technical  Bulletin  6,  page  2,  1903. 


HOW    TO    CONTROL    THIS    PEST. 


15 


The  Pimplas  are  common  parasites  in  Connecticut,  P.  con- 
quisitor  Say  shown  in  figure  13  being  one  of  the  commonest.  Of 
354  cocoons  collected  at  Stonington  this  season,  140  gave  ichneu- 
mon flies,  7  Tachinid  flies,  and  the  moths  emerged  from  207 
cocoons. 


Figure  13. — A  parasite  Pinipla  conquisitor  Say.     Natural  size. 

The  bacterial  disease  or  "wilt"  has  been  very  common  and 
the  caterpillars  are  sluggish  and  flabby,  and  die  on  the  outside 
of  the  trees  or  nests  in  a  shrunken  condition.  Several  predaceous 
insects,  including  the  larger  ground  beetles  of  the  genus  Calosoma, 
and  the  soldier  bugs  of  the  genus  Podisus,  as  well  as  two  other 
sucking  bugs,  Perillus  claiidus  Say,  and  Diplodus  luridiis  Stal., 
feed  upon  the  caterpillars. 

Birds  are  important  factors  in  the  control  of  this  pest,  the 
cuckoos  playing  a  prominent  part.  The  crow,  chickadee,  oriole, 
chipping  sparrow,  yellow  warbler,  and  red-eyed  vireo  are  other 
birds  that  feed  upon  the  caterpillars. 

Control  Measures. 

Destroying  the  Eggs.  Much  can  be  done  through  the  winter 
months  in  destroying  the  egg-masses.  When  the  trees  are  bare 
these  can  be  seen  near  the  ends  of  the  twigs,  and  may  easily 


Figure  14. — Tree  pruners. 


1 6      CONNECTICUT    EXPERIMENT    STATION,    BULLETIN    NO.    IJJ. 

be  clipped  off  by  means  of  a  tree  pruner  having  a  long  handle, 
(see  figure  14),  which  enables  the  operator  to  reach  and  cut 
off  the  egg-masses  while  standing  upon  the  ground.  These 
should  then  be  gathered  and  burned. 

Removing  the  Nests. 

Brushing.  Many  years  ago  the  writer  used  to  be  sent  through 
the  orchards  with  a  brush  mounted  on  the  end  of  a  pole  to 
remove  the  nests  from  the  trees  in  the  early  morning  or  on  a 
cloudy  day  when  the  caterpillars  were  in  them. 

The  brush  was  made  of  stiff  bristles  twisted  in  heavy  wire  and 
trimmed  to  the  shape  of  a  cone  about  six  inches  long.  It  was 
made  for  the  purpose,  and  worked  admirably. 

The  operator  stands  upon  the  ground,  inserts  the  point  of 
the  brush  in  the  nest  and  gives  it  a  few  turns,  and  the  entire 
nest  with  contents  is  wound  upon  the  brush.  The  caterpillars 
may  then  be  easily  destroyed  by  crushing  upon  the  ground. 

During  recent  )^ears  I  have  not  been  able  to  find  this  brush 
on  the  market,  but  Geo.  S.  Leiner  &  Co.  of  1250  Brook  avenue. 
New  York,  has  been  making  some  samples  after  my  specifications 
and  will  be  prepared  to  manufacture  it  in  the  future  if  there 
is  a  demand  for  it.  The  cost  will  be  less  than  fifty  cents  at 
wholesale  or  even  in  dozen  lots.  Local  dealers  and  seedsmen 
should  procure  a  supply  and  be  ready  to  sell  them  to  fruit 
growers  next  spring.  The  appearance  of  the  brush  is  shown 
in  figure  15. 


Figure  15. — A  caterpillar  brush. 


Burning,  Some  fruit  growers  practice  burning  the  nests  on 
the  trees  and  for  this  purpose  an  asbestos  torch  has  been  designed 
and  manufactured.  The  torch  is  filled  or  covered  with  kerosene, 
lighted,  and  held  under  the  nest  when  the  caterpillars  are  inside. 
We  do  not  recommend  burning,  because  there  is  danger  of 
severe  injury  to  the  tree.     Where  the  nests  are  near  the  ends 


HOW    TO    CONTROL    THIS    PEST.  1 7 

of  the  branches  the  damage  may  be  very  shght,  but  as  the  tent- 
caterpillars  often  make  their  tent  at  the  fork  of  comparatively 
large  branches,  it  cannot  be  burned  without  danger  of  killing 
these  branches.  Brushing  off  the  nests  with  a  caterpillar  brush 
is  just  as  expeditious  as  burning  and  there  is  no  danger  of 
injuring  the  trees. 

Spraying. 

Where  the  orchardist  practices  early  spraying  no  other  remedy 
need  be  considered.  Lead  arsenate  or  Paris  green,  with  or  without 
Bordeaux  mixture,  applied  to  the  foliage  will  kill  the  caterpillars. 
The  chief  difficulty  lies  in  the  fact  that  some  of  the  caterpillars 
hatch  and  begin  feeding  as  soon  as  the  first  leaves  appear  and 
before  there  is  really  any  leaf-surface  to  poison ;  some  danger 
may  be  done  before  spraying  begins.  But,  as  the  caterpillars 
eat  very  little  at  first,  this  damage  is  not  liable  to  be  serious. 
These  early  colonies  may  be  brushed  from  the  trees,  and  the 
spray  depended  on  to  kill  the  later  ones. 

Three  pounds  of  lead  arsenate  or  half  pound  of  Paris  green 
should  be  used  for  each  50  gallons  of  water  or  the  same  quantity 
of  Bordeaux  mixture.  Where  Paris  green  is  used  without 
Bordeaux  mixture,  three  pounds  of  fresh  lime  to  one  of  poison 
should  be  used  to  prevent  burning  the  leaves.  As  the  Bordeaux 
mixture  contains  plenty  of  lime,  no  more  is  needed  in  connec- 
tion with  it.  Lead  arsenate  is  perfectly  insoluble  in  water,  does 
not  injure  foliage,  and  therefore  does  not  need  the  addition  of 
lime.  Paris  green  contains  a  little  free  acid  which  is  soluble  in 
water,  and  which  unless  neutralized  may  burn  the  foliage. 

Community  Effort. 

Through  cooperation  any  insect  pest  can  be  checked.  It  is 
usually  the  careless  man  who  breeds  destructive  insects  for  his 
neighborhood.  Each  property  owner  and  tenant  should  take 
care  of  such  matters  on  the  land  which  he  owns  or  controls. 
In  some  European  countries,  he  is  compelled  to  remove  all 
destructive  pests  from  his  trees  and  shrubs,  and  similar  laws  are 
in  force  in  Massachusetts,  New  Hampshire,  and  Maine  regarding 
the  gypsy  and  brown-tail  moths.  If  the  owner  or  tenant  fails 
to  do  this,  it  is  done  by  the  town  or  by  the  state  and  he  pays 
the  cost  as  taxes. 


1 8      CONNECTICUT    EXPERIMENT    STATION,    BULLETIN    NO.    IJJ. 

Many  writers  advise  the  destruction  of  the  wild  cherry  and 
seedling-  apple  trees,  which  harbor  the  tent-caterpillar  along  the 
hedgerows  and  roadsides. 

If  not  destroyed,  the  owner  should  certainly  care  for  these 
trees  to  the  extent  of  keeping  them  free  from  insects,  and  not 


Figure  i6. — Sacks  filled  with  nests  ready  to  be  burned. 
Tent-Caterpillar  nest. 


Newtown. 


allow  them  to  be  a  menace  to  his  neighbor  or  the  orchards  of 
the  vicinity. 

Professor  Weed  recommends  that  children  be  given  a  small 
bounty  for  gathering  egg-masses  and  cites  a  case  in  Newfields, 
N.  H.,  where  they  were  offered  ten  cents  per  hundred  clusters, 
by  the  village  improvement  society.  8,250  egg-masses  were 
collected,  and  if  each  cluster  contained  150  eggs,  which  is  a 
small  average,  1,237,500  eggs  were  destroyed  at  a  cost  of  $8.25.* 

An  interesting  contest  was  conducted  in  1913,  by  Mr.  Leonard 
M.  Johnson,  principal  of  the  high  school  at  Newtown,  Conn., 
who  offered  a  prize  of  $5.00  to  the  boy  or  girl  bringing  in  the 
greatest   number   of   nests.     Second   and   third   prizes   of   $3-00 


*  Division  of  Entomology,  U.  S.  Dept.  Agriculture,  Bull.  17,  new  Series, 
page  "JT,  1898. 


SUMMARY.  19 

and  $1.00  respectively  were  also  offered.  All  nests  were  to  be 
cleaned  up  carefully  and  gathered  at  dusk  or  early  morning  when 
the  caterpillars  were  in  them.  The  results  were  very  satisfac- 
tory. It  was  a  hard  fought  contest  and  16,864  nests  were 
gathered  weighing  about   1,300  pounds.     The  winners  were: — 

Robert  Fairchilds,   ist  prize,  4,000  nests. 
Wilbur  Olmstead,    2d       "       3,6/5      " 
Russell  Wheeler,     3d       "       3,416      " 

Mr.  Johnson  took  charge  of  the  nests  brought  in  each  morning 
and  burned  them  at  a  bonfire.  Figure  16  shows  the  sacks  of 
nests  brought  to  school  at  one  time. 

A  similar  contest  in  gathering  the  egg-clusters  during  the 
winter  might  be  held  in  every  country  school  and  would 
materially  check  the  pest. 


SUMMARY. 


1.  The  apple-tree  tent-caterpillar,  a  native  insect  and  one  of  the 
chief  leaf-eating  enemies  of  the  orchard,  has  been  very  abundant 
throughout  Connecticut  the  present  season  and  has  injured  fruit 
trees  by  defoliating  them  in  May.  Wild  cherry  is  probably  the 
natural  food  of  the  species,  but  when  abundant  it  attacks  apple  and 
other  fruit  trees. 

2.  Eggs  are  laid  on  the  twigs  of  the  food  plant  in  summer  and 
hatch  the  following  April.  After  a  few  days  the  young  caterpillars 
form  on  the  branches  a  nest  in  which  they  live,  going  out  from  it 
to  feed.  They  are  always  within  the  nest  at  night  and  in  cloudy 
weather.  They  become  full-grown  in  about  six  weeks  and  spin  white 
silken  cocoons  from  which  the  adults  emerge  two  weeks  later. 

3.  The  small  grey  eggs  are  deposited  in  masses  of  200  or  more 
encircling  the  twigs,  and  are  covered  with  a  brownish  substance. 
The  full-grown  caterpillar  is  over  two  inches  long,  black  above  and 
below,  and  blue  on  the  sides,  with  a  white  stripe  along  the  back. 
It  is  thinly  covered  with  light  brown  hairs.  The  white  cocoon  is 
about  one  inch  in  length  and  half  an  inch  in  thickness.  The  adult 
is  a  reddish-brown  moth  with  two  whitish  stripes  extending  obliquely 
across  each  fore  wing. 

4.  The  species  is  usually  held  in  check  by  its  natural  enemies,  which 
consist  of  several  kinds  of  birds,  parasitic  insects  and  a  bacterial 
disease. 

5.  The  remedies  are:  to  gather  and  destroy  the  egg-masses  during 
the  winter  months;  an  effective  method  of  accomplishing  this  is  to 
offer  a  bounty  or  prizes  to  school  children  for  them;    spray  when  the 


20      CONNECTICUT    EXPERIMENT    STATION,    BULLETIN    NO.    I77. 

leaves  appear,  using  three  pounds  of  lead  arsenate  or  one-half 
pound  of  Paris  green  to  50  gallons  of  water  or  Bordeaux  mixture; 
if  impracticable  to  spray,  brush  off  the  nests  as  soon  as  they  can  be 
found,  choosing  the  early  morning  or  cloudy  weather,  when  the  cater- 
pillars are  inside  the  nest;  burning  the  nests  on  the  trees  is  not 
to  be  recommended. 


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